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Amazon Elastic Compute Cloud
User Guide for Windows Instances

Instance Volume Limits

The maximum number of volumes that your instance can have depends on the operating system. When considering how many volumes to add to your instance, you should consider whether you need increased I/O bandwidth or increased storage capacity.

Linux-Specific Volume Limits

Attaching more than 40 volumes can cause boot failures. Note that this number includes the root volume, plus any attached instance store volumes and EBS volumes. If you experience boot problems on an instance with a large number of volumes, stop the instance, detach any volumes that are not essential to the boot process, and then reattach the volumes after the instance is running.

Important

Attaching more than 40 volumes to a Linux instance is supported on a best effort basis only and is not guaranteed.

Windows-Specific Volume Limits

The following table shows the volume limits for Windows instances based on the driver used. Note that these numbers include the root volume, plus any attached instance store volumes and EBS volumes.

Important

Attaching more than the following volumes to a Windows instance is supported on a best effort basis only and is not guaranteed.

Driver Volume Limit

AWS PV

26

Citrix PV

26

Red Hat PV

17

We do not recommend that you give a Windows instance more than 26 volumes with AWS PV or Citrix PV drivers, as it is likely to cause performance issues.

To determine which PV drivers your instance is using, or to upgrade your Windows instance from Red Hat to Citrix PV drivers, see Upgrading PV Drivers on Your Windows Instances.

For more information about how device names related to volumes, see Mapping Disks to Volumes on Your Windows Instance.

C5 and M5 instances support a maximum of 28 attachments, and every instance has at least one ENI attachment. If you have no additional ENI attachments on a C5 or M5 instance, you could attach 27 EBS volumes. For information about ENI, see http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/using-eni.html.

Bandwidth versus Capacity

For consistent and predictable bandwidth use cases, use EBS-optimized or 10 Gigabit network connectivity instances and General Purpose SSD or Provisioned IOPS SSD volumes. Follow the guidance in Amazon EC2 Instance Configuration to match the IOPS you have provisioned for your volumes to the bandwidth available from your instances for maximum performance. For RAID configurations, many administrators find that arrays larger than 8 volumes have diminished performance returns due to increased I/O overhead. Test your individual application performance and tune it as required.